UNS: Taking Advantage of Metal Interpenetration to Improve the Performance of Conjugated Polymer/Fullerene-Based Photovoltaics

项目编号：1510353太阳代表着地球上最丰富的潜在可持续能源。利用吸收光的有机聚合物将光转化为电能的太阳能电池——有机光伏（OPV）装置——为可再生能源发电提供了一条潜在的低成本途径。然而，为了达到与其他太阳能光伏技术相当的水平，有机太阳能电池必须提高其能量转换效率，超过目前10.5%的世界纪录。该项目的目标是将金属纳米颗粒添加到有机太阳能电池的活性层中，以可能提高太阳能转换效率。OPV器件的活性层由导电聚合物和纳米结构碳组成。如果金属纳米颗粒在正确的位置，它们将通过一个称为等离子共振的复杂过程增强光吸收，并最终提高太阳能转换效率。该项目的一个关键创新是，金属纳米颗粒将在活性层内的精确位置形成，从而实现这一过程。作为与该项目相关的教育活动的一部分，首席研究员参与了一个项目，该项目将纳米技术主题引入整个洛杉矶地区的高中教室，为高中教师举办一系列研究生研讨会。该奖学金资助的研究生将开发并举办以有机太阳能电池为特色的太阳能研讨会。制造有机光伏器件的主要技术挑战是精确控制吸光聚合物（电子供体）和富勒烯（电子受体）的纳米尺度空间分布，以优化电荷分离和光电流收集。此外，在器件制造过程中可能会出现其他复杂因素。例如，导电金属通过热蒸发沉积在有机聚合物层的顶部，作为电触点。据推测，这些蒸发的金属很容易穿过富勒烯，并在任何位于聚合物层顶部的富勒烯下留下一层金属纳米颗粒，从而对设备性能产生意想不到的影响，而这些影响迄今为止一直被忽视。初步数据支持这一假设，本研究的总体目标是确定金属互穿对聚合物基光伏器件性能的影响，然后制定有针对性地操纵金属纳米粒子互穿的策略，通过等离子体光吸收增强来提高器件性能。在本研究中，将使用实验和计算方法来理解这些过程。顺序处理，即供体（导电聚合物）和受体（富勒烯）层在不同的步骤沉积，将用于控制OPV活性层内富勒烯的垂直分布。透射电子显微镜，结合椭偏仪和中子反射法，将用于研究金属穿透富勒烯的条件。这些信息将用于制定合成策略，以控制相互渗透金属的分布，并最终形成金属纳米颗粒的大小和位置。介电常数、等离子体吸收增强和激子猝灭测量将在金属纳米颗粒浸没的活性层上进行，这些基本的光电特性测量将与器件性能的整体测量相关，包括太阳能转换效率、外部量子效率和光电流/光电压瞬变。麦克斯韦完整解的互补模拟？S方程与标准漂移扩散解将执行与金属纳米粒子在活性层，以帮助理解和解释这些实验结果。研究结果将为同时提高OPV器件的制造和性能提供有针对性的方法。

PI: Benjamin J. Schwartz Proposal Number: 1510353The sun represents the most abundant potential source of sustainable energy on earth. Solar cells that use light-absorbing organic polymers to convert light to electricity - organic photovoltaic (OPV) devices - offer a potentially low-cost route for renewable electricity production. However, in order to achieve parity with other solar photovoltaic technologies, organic solar cells must increase their power conversion efficiency past the current 10.5% world record. The goal of this project is to add metal nanoparticles into the active layer of the organic solar cell to possibly enhance solar energy conversion efficiency. The active layer of the OPV device consists of the conducting polymer and nanostructured carbon. If the metal nanoparticles are in the right place, they will enhance light absorption, and ultimately solar energy conversion efficiency, through a complex process called plasmonic resonance. A key innovation of this project is that that metal nanoparticles will be formed at precise locations within the active layer to enable this process. As part of the educational activities associated with this project, the principal investigator participates in a program where nanotechnology topics are brought to high school classrooms throughout the greater Los Angeles area in a series of graduate student-run workshops for high school teachers. The graduate student supported by this grant will develop and conduct workshops on solar energy featuring organic solar cells.A major technical challenge with the fabrication of organic photovoltaic devices is to precisely control the nanoscale spatial distribution of the light-absorbing polymer (electron donor) and fullerene (electron acceptor) to optimize charge separation and photocurrent collection. Furthermore, other complicating factors may occur during device fabrication. For example, conductive metals are deposited on the top of the organic polymer layer by thermal evaporation to serve as an electrical contact. It is hypothesized that these evaporated metals easily move through the fullerenes and leave a layer of metal nanopart¬icles underneath any fullerenes that reside at the top of the polymer layer, creating unintended consequences to device performance that have been overlooked to date. Preliminary data supports this hypothesis, and the overall goals of this proposed research are to determine the effects of metal interpenetration on the performance of polymer-based PV devices, and then develop strategies to purposely manipulate metal nanoparticle interpenetration to improve device performance through plasmonic optical absorption enhancement. In the proposed research, experimental and computational approaches will be used to understand these processes. Sequential processing, where the donor (conducting polymer) and acceptor (fullerene) layers are deposited in separate steps, will be used to control the vertical fullerene distribution within the OPV active layer. Transmission electron microscopy, in combination with ellipsometry and neutron reflectometry, will be used to study the conditions by which metals penetrate through fullerenes. This information will be used to develop synthesis strategies to control the distribution of interpenetrated metal, and ultimately the size and position of the metal nanoparticles that are formed. The dielectric constant, plasmonic absorption enhancement, and exciton quenching measurements will performed on the metal nanoparticle impregnated active layer, and these fundamental optoelectronic property measurements will be correlated to overall measurements of device performance, including solar energy conversion efficiency, external quantum efficiency, and photocurrent/photovoltage transients. Complementary simulations that couple full solutions of Maxwell?s equations with standard drift-diffusion solvers will be performed with metal nanoparticles in the active layer to help to understand and interpret these experimental results. The research outcomes will suggest purposeful ways to simultaneously enhance OPV device fabrication and performance.